When Boulder, Colorado, resident Donna Coughlin glanced out of her window in the middle of the night, she saw something quite strange: someone had put a 500-lb sculpture in her front yard.

It came in the middle of the night -- 15 feet tall, lit up by white lights, antennae protruding from its head -- set down in the middle of Donna Coughlin's front yard with nary a blade of grass put out of place.

"It startled me so much," said Coughlin, who spotted the object out the window of her Boulder home around 1:30 a.m. Saturday. "I said to myself, 'What in the dickens is that?'"

The hulking visitor stands sentry on her lawn at the corner of 25th Street and Valmont Road, quiet and still. It doesn't look as though it means to do Coughlin any harm. It simply looks like it's there to ...

"Who knows?" the 80-year-old Boulder native said Monday. "I have no idea."

Neither do police, who paid a visit to Coughlin's home over the weekend to try to determine how and why a towering steel-and-cement sculpture suddenly appeared on her lawn.

"Detectives can't figure out how they got the darn thing in there without leaving any drag marks behind," said Cmdr. Kim Stewart with the Boulder Police Department. "It's odd -- it's like it's perfectly placed there."